This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Tuberculosis (TB) remains a major threat to global public health and infection with Mycobacterium tuberculosis (Mtb) is estimated to result in over 2 million deaths annually. In order to develop new vaccines and drugs for TB, we need to understand how Mtb evades innate immunity and survives in hostile immune environments. A central feature of Mtb pathogenesis is its ability to grow within macrophages, modulate their activities and interfere with microbicidal functions. We have identified a cell envelope-localized lipoprotein encoding a serine hydrolase, Rv2224c, which is critical for Mtb virulence in vivo, survival in macrophages and resistance to cell envelope-directed stresses. We have named this protein Hip1 (Hydrolase important for pathogenesis 1). We demonstrate that Hip1 suppresses innate immune responses;hip1 mutants induce enhanced proinflammatory responses downstream of Toll-like receptor (TLR)-signaling in macrophages. We hypothesize that Hip1 modifies cell envelope or secreted substrates to modulate innate immunity and host defense. The focus of this project is to understand how Hip1 suppresses host innate immune pathways and determine the molecular and biochemical mechanisms for Hip1 function.